High temperature electrical cable

ABSTRACT

A high temperature electrical cable comprising generally three parts is disclosed, namely a central conductor, a covering of insulating material applied over the central conductor and an outer protective sleeving applied over the covering of insulating material. The central conductor is made of stranded or solid metal capable of essentially maintaining its useful service at high temperature. The covering of insulating material consists of at least one inner layer of inorganic high temperature material providing essentially complete coverage of the conductor and a smooth base for the subsequent layers, at least two layers of primary dielectric material consisting of mica tapes made from reconstituted mica sheets impregnated with carborane siloxane polymers, and an outer layer of inorganic high temperature material over the mica tapes such as to provide essentially complete coverage of the primary dielectric layers. The outer protective sleeving is achieved either by knitting or braiding one or more fine high temperature resistant wires onto the covering of insulating material.

United States Patent 119 Bayles et a1.

1 1 HIGH TEMPERATURE ELECTRICAL CABLE [75] Inventors: Francis Derrick Bayles, Montreal;

Michael Alan Dudley, Beaconsfield; John C. Metzler, Pierrefonds all of Canada [73] Assignee: Canada Wire and Cable Limited,

Toronto, Canada 22 Filed: July 15, 1974 [21] Appl No.: 488,409

[30] Foreign Application Priority Data June 21, 1974 Canada 203090 [52] U.S. Cl 174/102 R; 174/] 105; 174/120 C; 174/121 A; 174/1226 [51] Int. Cl .v HOIb 7/18; H01b 3/04 [581 Field of Search 174/102 R. 102 A, 110 S, 174/110 R. 120 R 120C, 121 A, 122 R 122 G, 124 R, 124 G, 124 GC, 126 R, 126 CP,

128. 25 C, 105 R, 106 R [56] References Cited UNITED STATES PATENTS 2.595729 6/1952 Swiss et a1 174/121 SR 2,739.638 3/1956 Lewis et a1. 174/120 R UX 2829,19] 4/1958 Rogers, Jr. 174/122 R UX 31142743 7/1962 Jones 1 1 1 1 1 1 1 .t 174/124 G X 3.069.302 12/1962 Lewis et all 1. 174/124 R X 1265,8011 8/1966 Binch I 1 1. 174/105 R 3,303,270 2/1967 Shelton. Jr...v 174/124 R X 3,425,865 2/1969 Shelton, Jr 174/120 R X 1588.318 6/1971 Ollis 174/1105 X 1 51 Aug. 19, 1975 P7771207) E.\'amiuerArthur T. Grimley Attorney, Agent, or FirmFleit & Jacobson [57] ABSTRACT A high temperature electrical cable comprising generally three parts is disclosed, namely a central conductor, a covering of insulating material applied over the central conductor and an outer protective sleeving applied over the covering of insulating material. The central conductor is made of stranded or solid metal capable of essentially maintaining its useful service at high temperature. The covering of insulating material consists of at least one inner layer of inorganic high temperature material providing essentially complete coverage of the conductor and a smooth base for the subsequent layers, at least two layers of primary dielectric material consisting of mica tapes made from reconstituted mica sheets impregnated with carborane siloxane polymers. and an outer layer of inorganic high temperature material over the mica tapes such as to provide essentially complete coverage of the primary dielectric layers. The outer protective sleeving is achieved either by knitting or braiding one or more fine high temperature resistant wires onto the covering of insulating material.

19 Claims. 5 Drawing Figures INORGANIC HIGH TEMPERATURE HIGH TEMPERATURE RESISTANT METAL CONDUCTOR IMPREGNATED MICA TAPE PRIMARY C OONSISTING OF MICA MPREGNATED WITH NE SILOXANE POLYMERS RESISTANT BRAIDED FIBERS HIGH TEMPERATURE RESISTANT xmrreo BRAIDED METALLIC l8 OUTER SLEEVING PATENTEUAUBI 8M5 3,900 701 INORGANIC men TEMPERATURE HIGH TEMPERATURE RE ANT BRAIDED FIBERS 3 ST RESISTANT KNITTED 0R BRAIDED METALLIC l6 l8 OUTER SLEEVING FIG. I

HIGH TEMPERATURE RESISTANT METAL CONDUCTOR IMPREGNATED M|cA TAPE PRIMARY DIELECTRIC CONSISTING 0F MICA SHEETS IMPREGNATED WITH CARBORANE SILOXANE POLYMERS FIG. 3

POLYMERIC MATERIAL POLYMERIC MATERIAL POLYMERIC MATERIAL HIGH TEMPERATURE ELECTRICAL CABLE This invention relates to a high temperature electrical cable.

With the advent of more severe aircraft environments, expected to be encountered in supersonic transports and tactical aircraft operating considerably in excess of the speed of sound, there is an increasing need for large volumes of economically produced flexible cable which is small in diameter, lightweight, capable of carrying 600 volts or more, and capable of performing at l,000F or higher for extended periods of time.

Additionally, the operational conditions are such that the electrical cable should exhibit little or no tendency to smoke or fume, be relatively insensitive to moisture absorption, shock and impact and exhibit a minimum of abrasion destruction of the insulating layer or layers during vibration and flexing, all of these both before and after exposure to l,000F and greater.

Prior art insulated cable allegedly useful for this purpose has been successful in only some of the requirements, showing, for example, embrittlement, evolution of degradation products and loss of flexibility upon exposure to l,000F and greater.

Some of the prior art high temperature cables, such as the one disclosed in Canadian Pat. No. 870,247 issued May 4, 1971, are covered with an armoured sheathing which greatly reduces the flexibility of such cables.

It is therefore the object of the present invention to provide a high temperature cable which overcomes the above disadvantages of the prior art cables.

The high temperature cable, in accordance with the invention, comprises generally three parts: a central conductor, a covering of insulating material over the central conductor, and an outer protective sleeving over the covering of insulating material. The central conductor is made of stranded or solid metal capable of essentially maintaining its useful service at high temperature. The covering of insulating material consists of at least one inner layer of inorganic high temperature material providing essentially complete coverage of the conductor and a smooth base for the subsequent layers, at least two layers of primary dielectric material consisting of impregnated mica tapes made from reconstituted mica sheets impregnated with carborane siloxane polymers, and an outer layer of inorganic high temperature material over the mica tapes such as to provide essentially complete coverage of the primary dielectric layers. The outer protective sleeving is achieved either by knitting or braiding one or more fine high temperature resistant wires onto the covering of insulating material.

The central conductor may consist of a central metal core cladded with a dissimilar metal, selected from the group consisting of nickel clad copper, nickel clad silver, nickel alloy clad silver, nickel alloy clad copper,

and stainless steel clad copper. It may also be made of rhodium or other suitable refractory metal.

The inner and outer layers of inorganic high temperature material may advantageously be braided fibers selected from the group consisting of quartz, leached glass, boron free glass and the like or combinations of them.

The mica tapes used in the primary dielectric layers may optionally be reinforced with a backing of any one of the above mentioned braided fibers applied as unidi- 2 rectional thread or woven construction and impregnated with a polymeric material. Such polymeric material may be selected from the group consisting of carborane siloxane polymers, poly(siloxanes), or any other flexible inorganic polymers.

The mica tapes are preferably applied as lapped, open helically wound tapes in the same or opposite lay in different layers in order to give essentially complete coverage of the inner layer of high temperature material and a functional dielectric strength of 1,000 volts or more.

The metallic wires used in the outer protective sleeving may advantageously be made of stainless steel, nickel alloy or any other high temperature resistant material.

The invention will now be disclosed, by way of example, with reference to preferred embodiments thereof illustrated in the accompanying drawing wherein:

FIG. 1 illustrates an electrical cable in accordance with the invention;

FIGS. 2 and 2a illustrate an elevation and a side view respectively of a portion of the tape which may be used for making the cable of FIG. 1; and

FIGS. 3 and 3a illustrate another configuration of a tape which may be used for making the cable of FIG. 1.

Referring to the drawing, there is shown a high temperature electrical cable comprising a central conductor 10 which may be a solid metal conductor or made of a plurality of metal wires stranded together. As mentioned previously, the metal of the conductor must be capable of maintaining its useful service at high temperature. It may consist of a central core cladded with a dissimilar metal, such as nickel clad copper, nickel clad silver, nicekl alloy clad copper, nickel alloy clad silver and stainless steel clad copper. It may also be made of rhodium or any other suitable refractory metal. In a preferred but not limitative embodiment of the invention, the conductor was a solid conductor made of a fine silver core cladded with a nickel alloy sheath representing a cross-section area for the sheath of between 25 and 50 percent, and preferably in the range of 40-50 percent of the total cross-section area. The nickel alloy used was one known under the Trademark Inconel 600 sold by International Nickel Company. It is to be understood that other conductor conflgurations capable of maintaining their useful service at high temperature may be used.

The conductor 10 is then covered with at least one layer of inorganic high temperature material 12. The purpose of the inorganic high temperature material is to give essentially complete coverage of the conductor and provide a smooth surface for subsequent layers and thus improve the flexibility of the cable. In a preferred embodiment of the invention, such high temperature material was in the form of braided fibers selected from the group consisting of quartz, leached glass, boron free glass and the like or combinations of them. Some commercial sources of these fibers include the ones known under the trademarks S glass of Owens Corning, Refrasil of Hitco, Sil-Temp of Haveg, and AstroQuartz of J.P. Stevens. Braiding is achieved at between 10 and 18 fiber picks per inch, for a nominal 0.03 in. cord on a 12 AWG conductor. One or two layers of braided fibers were found to be sufficient but it is to be understood that plural layers may be used if necessary, more particularly if other materials than braided fibers are employed. It is to be understood that other inorganic high temperature materials could be used in place of braided fibers.

At least two layers of primary dielectric materials consisting of impregnated mica tapes 14 made of reconstitued micaceous sheets impregnated with car- 4 Layer 14 of primary dielectric insulating material is covered with a further layer 16 of inorganic high temperature material similar to inner layer 12 so as to give essentially complete coverage of the primary dielectric borane siloxane polymers are then helically wound layer 14. over the layer 12. In the preferred, but not limitative, FIGS. 2 and 2a illustrate an elevation and side view embodiment of the invention, the primary dielectric respectively of a portion of a tape 14 reinforced with a layer consisted of three layers of lapped, open helically backing of braided fibers applied as unidirectional wound impregnated mica tapes, 2 thousandths of an threads whereas FIGS. 3 and 3a illustrate correspondinch thick by /4 inch wide which had been previously l0 ing views of a tape 14 reinforced with a backing of impregnated with a cured decaborane-siloxane polybraided fibers 15 applied as a woven construction. mer known under the trademark Dexsil 300 sold by Finally, an outer sleeving 18 achieved by knitting or Olin Mathieson Company at an approximate loading of braiding one or more fine, high temperature resistant 2 to 25 percent, preferably 6 to l2 percent by weight metal wires, is applied over the previously assembled on weight of mica paper. These tapes were laid in the configuration. As mentioned previously, such a wire same direction or in opposite directions in different laycould be made of stainless steel or nickel alloys. In a ers so as to achieve essentially complete coverage of preferred embodiment, the sleeving was a knitted the inner layer 12 and a dielectric strength of 1,000 sleeve made of lnconel 600 wire. It is to be understood volts or more, under a variety of environmental expothat other high temperature resistant wires would be sure conditions. It is to be understood that the number 20 suitable. [t is important to note that this type of outer of layers of mica tapes may be higher than two. lt is also protection allows greater flexibility of the wire, smaller to be understood that other carborane siloxanes may wire diameter, and lighter weight than other armoured also be used as impregnants for reconstituted mica sheathings known in the prior art such as the one dissheets. Some of the carborane siloxane materials that closed in Canadian Patent No. 870,247 issued May 4, have been found particularly good as impregnating ma- 197 l. terials for reconstituted micaceous sheets include Testing was carried out on the above mentioned predecaborane siloxane polymers such as the ones known ferred embodiment consisting of a 12 AWG conductor under the trademark Dexsil and sold by Olin Mathieson of a fine silver core oversheathed with lnconel 600, a Company, pentaborane siloxane polymers such as the first inorganic layer of braided fibers known as Refrasil ones known under the trademark Pentasil and sold by C-l00-2, a primary dielectric insulation consisting of Chemical Systems lnc., and mixed meta and para three layers of lapped, open helically wound impregdecaborane siloxane polymers such as the ones known nated mica tapes of 0.002 of an inch thick by A inch under the trademark Ucarsil and belonging to Union wide previously impregnated with a cured decaborane- Carbide Corporation. Copolymers of decaand pentasiloxane polymer (Dexsil 300) at an approximate loadborane siloxane polymers as well as physical combinaing of l0 percent by weight on weight of mica paper, tions of decaand penta-borane siloxane polymers have another inorganic layer of braided fiber of Refrasil C- also been advantageously used. These mica-impregnant 100-2, and a protective sleeving of knitted 0.0045 inch combinations result in a primary dielectric material diameter lnconel 600 wire. showing excellent initial flexibility and tensile strength, The results given in the Table have been obtained excellent dielectric strength, low weight change and against aperformance requirement noted in brackets:

TABLE PERFORMANCE PROPERTIES OF PREFERRED EMBODIMENT Test Condition Diclcctric'" Dielectric" lnsulation Withstand Breakdown in Resistance in Rcq uircment Kilovolts megohms/ft 2.2 KV for 5 sec.) (Requirement (Requirement L2 KV) l.0 megohm/ft.)

Mandrel and thcnnal shock passed 4.] As fabricated passed 1.3 X l0 76F/50% RH passed 5.0 76F/l00% RH passed 4.4 At l250F passed 2.4 3.0 76F/5U% RH passed 11.4 x 10 At -F passed 4.8 76F/l00% RH 8.3 X 10 At I250F 3.5 After 800 hrs. at 1250F 2.0

"'l'csl performed in accordance with ASTM Dl49 *"l'csl performed in accordance with ASTM D257 Vibration: (20 g, 10-2000 cps) passed Mechanical shock: (50 g, l I I millisecond] passed Abrasion resistance; .lanco Abrader, 30 in. of garnet tape 12 in. garnet tape) Mnndrcl flexibility: (wind 20 X wire diameter] passed Ill x moisture pick-up and significantly better retention of these properties after high temperature exposure, in

This construction also carried an electrical load in 1,200 volts R.M.S. without breakdown for three hours in a direct flame of approximately l,O00C. Furthercomparison to other commercially available materials. 65 more, the insulation did not burn or smoke throughout Further references to specific properties and methods of construction of these composites may be found in US. application No. 488,408 filed July I5, 1974.

the duration of the exposure.

What is claimed is: l. A high temperature electrical cable comprising:

a. a central conductor made of a metal capable of essentially maintaining its useful service at high temperatures;

b. a covering of electrical insulating material applied over said conductor and consisting of at least one inner layer of inorganic high temperature material providing essentially complete coverage of said conductor and a smooth base for subsequent layers, at least two layers of primary dielectric material consisting of impregnated mica tapes made of reconstituted mica sheets impregnated with carborane siloxane polymers, and at least one outer layer of inorganic high temperature material over said impregnated mica tapes; and

c. an outer layer protective sleeving applied by knitting or braiding over said outer layer of inorganic high temperature material and consisting of at least one high temperature resistant metal wire.

2. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of solid metal.

3. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of plu' ral strands of metal.

4. A high temperature electrical cable as defined in claim 1, wherein the central conductor consists of a central metal core cladded with a dissimilar metal.

5. A high temperature electrical cable as defined in claim 4, wherein the central conductor is made of a metal selected from the class of metal consisting of nickel clad copper, nickel clad silver, nickel alloy clad copper, nickel alloy clad silver and stainless steel clad copper.

6. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of rhodium.

7. A high temperature electrical cable as defined in claim 1, wherein the conductor consists of a silver core protected by a nickel alloy sheath representing a crosssectional area for the sheath of between and 50 percent of the total cross-section area of the conductor.

8. A high temperature electrical cable as defined in claim 7, wherein the nickel alloy sheath represents a cross-sectional area for the sheath of preferably between 40 and 50 percent of the total cross-section area of the conductor.

9. A high temperature electrical cable as defined in claim 1, wherein the inner and outer layers of inorganic high temperature material are made of braided fibers selected from the group consisting of quartz, leached glass, boron free glass and the like and combinations thereof.

10. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are reinforced with a backing of fibers applied as unidirectional thread or woven construction and impregnated with a polymeric material.

1 l. A high temperature electrical cable as defined in claim 10, wherein the polymeric material used for impregnation of the backing may be selected from the group consisting of carborane siloxane polymers and poly (siloxanes).

12. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with decarborane siloxane polymers.

13. A high temperature electrical cable as defined in claim 1, wherein the impregnated tapes are made of reconstituted mica sheets impregnated with pentaborane siloxane polymers.

14. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with mixed meta-and para-decarborane siloxane polymers.

15. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with copolymers of decaand penta-borane siloxane.

16. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with physical combinations of decaand penta-borane siloxane polymers.

17. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are applied as lapped, open helically wound tapes applied in the same or opposite lay in the different layers in order to give essentially complete coverage of the wire and a functional dielectric strength of 1,000 volts or more.

18. A high temperature electrical cable as defined in claim 1, wherein the metallic wires of the outer sleeving are selected from the group consisting of stainless steel and nickel alloys.

19. A high temperature electrical cab e as defined in claim 1, wherein the central conductor is made of nickel alloy clad silver, the inner and outer layers of inorganic high temperature insulative material made of braided fibers, the primary dielectric layers made of lapped open helically wound tapes of reconstituted mica sheets impregnated with cured carborane siloxane polymers to approximately 10 percent weight loading on weight of mica tapes, and the protective sleeving made of nickel alloy high temperature resistant wire. 

1. A HIGH TEMPERATURE ELECTRICAL CABLE COMPRISING: A. A CENTRAL CONDUCTOR MADE OF A METAL CAPABLE OF ESSENTIALLY MAINTAINING ITS USEFUL SERVICE AT HIGH TEMPERATURES, B. A COVERING OF ELECTRICAL INSULATING MATERIAL APPLIED OVER SAID CONDUCTOR AND CONSISTING OF AT LEAST ONE INNER LAYER OF INORGANIC HIGH TEMPERATURE MATERIAL PROVIDING ESSENTIALLY COMPLETE COVERAGE OF SAID CONDUCTOR AND A SMOOTH BASE FOR SUBSEQUENT LAYERS, AT LEAST TWO LAYERS OF PRIMARY DIELECTRIC MATERIAL CONSISTING OF IMPREGNATED MICA TAPES MADE OF RECONSTITUTED MICA SHEETS IMPREGNATED WITH CARBONANE SILOXANE POLYMERS, AND AT LEAST ONE OUTER LAYER OF INORGANIC HIGH TEMPERATURE MATERIAL OVER SAID IMPREGNATED MICA TAPES, AND C. AN OUTER LAYER PROTECTIVE SLEEVING APPLIED BY KNITTING OR BRAIDING OVER SAID OUTER LAYER OF INORGANIC HIGH TEMPERATURE MATERIAL AND CONSISTING OF AT LEAST ONE HIGH TEMPERATURE RESISTANT METAL WIRE.
 2. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of solid metal.
 3. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of plural strands of metal.
 4. A high temperature electrical cable as defined in claim 1, wherein the central conductor consists of a central metal core cladded with a dissimilar metal.
 5. A high temperature electrical cable as defined in claim 4, wherein the central conductor is made of a metal selected from the class of metal consisting of nickel clad copper, nickel clad silver, nickel alloy clad copper, nickel alloy clad silver and stainless steel clad copper.
 6. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of rhodium.
 7. A high temperature electrical cable as defined in claim 1, wherein the conductor consists of a silver core protected by a nickel alloy sheath representing a cross-sectional area for the sheath of between 25 and 50 percent of the total cross-section area of the conductor.
 8. A high temperature electrical cable as defined in claim 7, wherein the nickel alloy sheath represents a cross-sectional area for the sheath of preferably between 40 and 50 percent of the total cross-section area of the conductor.
 9. A high temperature electrical cable as defined in claim 1, wherein the inner and outer layers of inorganic high temperature material are made of braided fibers selected from the group consisting of quartz, leached glass, boron free glass and the like and combinations thereof.
 10. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are reinforced with a backing of fibers applied as unidirectional thread or woven construction and impregnated with a polymeric material.
 11. A high temperature electrical cable as defined in claim 10, wherein the polymeric material used for impregnation of the backing may be selected from the group consisting of carborane siloxane polymers and poly (siloxanes).
 12. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with decarborane siloxane polymers.
 13. A high temperature electrical cable as defined in claim 1, wherein the impregnated tapes are made of reconstituted mica sheets impregnated with pentaborane siloxane polymers.
 14. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with mixed meta-and para-decarborane siloxane polymers.
 15. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with copolymers of deca- and penta-borane siloxane.
 16. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are made of reconstituted mica sheets impregnated with physical combinations of deca- and penta-borane siloxane polymers.
 17. A high temperature electrical cable as defined in claim 1, wherein the impregnated mica tapes are applied as lapped, open helically wound tapes applied in the same or opposite lay in the different layers in order to give essentially complete coverage of the wire and a functional dielectric strength of 1,000 volts or more.
 18. A high temperature electrical cable as defined in claim 1, wherein the metallic wires of the outer sleeving are selected from the group consisting of stainless steel and nickel alloys.
 19. A high temperature electrical cable as defined in claim 1, wherein the central conductor is made of nickeL alloy clad silver, the inner and outer layers of inorganic high temperature insulative material made of braided fibers, the primary dielectric layers made of lapped open helically wound tapes of reconstituted mica sheets impregnated with cured carborane siloxane polymers to approximately 10 percent weight loading on weight of mica tapes, and the protective sleeving made of nickel alloy high temperature resistant wire. 